Abstract: In order to solve the problem of large stock and difficult utilization of low-silicon iron tailings,lightweight foamed concrete was prepared by using low-silicon iron tailings from Yangjiawan tailings reservoir as mineral admixtures,cement as cementitious material and Al powder as foaming agent. The effects of cement dosage,water-to-material ratio,foaming agent Al powder dosage and activator CaO dosage on the performance of foamed concrete were investigated. The results showed that under the condition of iron tailings dosage of 55%,Al powder dosage of 0. 14%,CaO dosage of 5%,polypropylene fiber dosage of 0. 3%,foam stabilizer dosage of 0. 25% and water-to-material ratio of 0. 55,the lightweight foamed concrete with compressive strength of 1. 84 MPa,dry density of 768. 61 kg/ m3 and specific strength of 2. 394×10-3 Nm/ kg could be prepared after curing 28 days of constant temperature and humidity at 20±1 ℃. The comprehensive performance was good,which met the requirements of A08 dry density grade and C1 strength grade of JG/ T 266—2011 Foamed concrete. The mechanism analysis showed that the excessive increase of porosity would destroy the pore structure inside the products and had a negative impact on the strength of the products. The addition of iron tailings helped to mix the slurry,promoted the formation of Ca(OH)2,further created an alkaline environment for the slurry,and promoted the formation of hydration products such as ettringite and C—S— H gel. The interlaced distribution of these products and iron tailings would support the pore structure and improve the mechanical structure,so that the foamed concrete still showed good mechanical properties even at a low density.

Key words: low-silicon iron tailings,foamed concrete,mechanism,Al powder,specific strength